Lists: Adding and removing

fn main() {
    let cart = ["pen", "book"]
    cart.push("bag")
    print(cart)
    cart = cart.filter(item => item != "book")
    print(cart)
    print(cart.len())
}

["pen", "book", "bag"]["pen", "bag"]2

filter makes a new list of the items its test is true for. Assigning it back to cart removes the rest.

Two lists together

fn main() {
    const evens = [2, 4]
    const all = evens + [6, 8]
    print(all)
    print(evens)

    let log = ["start"]
    log += ["step 1", "step 2"]
    print(log)
}

[2, 4, 6, 8][2, 4]["start", "step 1", "step 2"]

• evens + [6, 8] is a new list: the items of the first, then those of the second. Neither changes.
• log += ["step 1", "step 2"] adds the items to the end of log, so like push it needs a let. When nothing else holds the list, it grows in place, without copying what it holds.
• Both lists hold the same type.

Taking the last item

pop() takes the last item out and gives it, or none for an empty list. It changes the list, so it needs a let too:

fn main() {
    let stack = [1, 2, 3]
    const top = stack.pop() ?? 0
    print(top)
    print(stack)

    let empty: [Int] = []
    print(empty.pop())
}

3[1, 2]none